B. pseudosulphureus

Boletus L.

Recent molecular studies have shown that Boletus in its current circumscription is likely an artificial grouping and it is possible that it will be split at some point into smaller genera. Note that Boletus impolitus and Boletus depilatus for practical reasons are retained here, although there is strong evidence that they are closely related to Xerocomus subtomentosus and its allies.

Fruitbody large to medium sized, boletoid, without veil and ring. Stipe solid, with surface usually covered with granules or network. Flesh variously coloured, changing or not when exposed to air. Tubes easily separable from each other, not tearing apart. Pores usually small and rounded.

Boletus pseudosulphureus Kallenb.

Description
Cap up to 15 cm, hemispherical then convex, flat-convex or almost flat, initially dry, velvety, later smooth, lemon to bright yellow, yellowish ochraceous, in young fruitbodies more or less uniformly coloured, later spotted brownish, strongly blueing when bruised, then blackening. Stipe clavate, concolorous with the cap, covered with scattered yellow to brownish granules, surface blueing and then blackening when bruised. Flesh lemon yellow, sometimes with dark red spots in the stipe base, blueing when exposed to air. Tubes lemon yellow to yellow with olivaceous tint, blueing when exposed to air. Pores concolorous with the tubes, blueing when bruised. Smell not distinctive. Taste slightly acid. Spores 12–16.5 × 4.5–6 μm, ratio 2.2–2.7. Pileipellis (the cap cuticle) a trichodermium of interwoven septate hyphae of cylindrical, not incrusted cells. Chemical reactions: hyphae of the stipe base inamyloid.

Similarity. Compare with Boletus luridiformis var. discolor, which has similarly coloured fruitbodies, but features orange pores.

Note. Some recent autorities reduce this species to a variety of Boletus luridiformis on the base of unpublished molecular studies. It is clear that the entity in question is close to Boletus luridiformis. Nonetheless, here I intend to keep it at species level until published study is available for this confusing group. This species was long time known under the name Boletus junquilleus (Quél.) Boud., but due to confusion in the past it will have to be abandoned in favor of Boletus pseudosulphureus. In fact the original description of Boletus junquilleus and the later illustration in Boudier’s Icones Mycologicae fit well the species in question. Especially in Britain the name B. junquilleus was applied to Boletus luridiformis var. discolor and this is exactly where this confusion came from.

Photographs

Fruitbodies of Boletus pseudosulphureus. Note the blackening of the fruitbodies when bruised or handled. (photo B. Assyov)